Many of these hazards call for the DM to pick random targets. This is because I don’t know the number of targets you might have in your own encounters. When trying to determine who might be targeted by a hazard, feel free to have all potential targets roll a d20. The lowest roll is the unlucky target.

Most of these hazards have effects which occur during each round of combat, while a few others have a more powerful effect which occurs once during combat.

Mundane

Mundane hazards are caused by nature or creatures without the aid of any supernatural forces like magic. Many of these hazards exist in our real world.

Avalanches

Avalanches can occur in areas where snow piles up on a slope, such as a mountain. When battle in an area with avalanche potential occurs roll a d4 at the end of each round of combat. On the roll of a 1 the avalanche covers a 30-foot-square area. Creatures in the area must make a DC 15 Dexterity saving throw. Creatures who fail take 14 (4d6) cold damage and 14 (4d6) bludgeoning damage and are knocked prone and restrained. A prone creature cannot stand until it ends the restrained condition by using its action to make a DC 15 Strength saving throw or another unrestrained creature uses its action to dig out the restrained creature ending the restrained condition. Creatures who succeed take only half damage and are knocked prone, but not restrained. The area where the avalanche occurred is considered difficult terrain and you stop rolling to see if an avalanche occurs at the end of each round.

Bone Piles

Deep in the lairs of monstrous creatures, adventurers might come across enormous piles of bones picked clean, the remnants of past meals. Bone piles count as difficult terrain. If combat occurs on a bone pile creatures have the potential to sink into the bones. When a creature ends its turn on a bone pile without moving from the spot where it started its turn, that creature takes 3 (1d6) piercing damage and is restrained. As an action a restrained creature can attempt to free itself and end the restrained condition with a DC 12 Strength saving throw.

Broken Ground

Broken ground is any uneven floor such as the craggy, cracked floor of an earthquake ruined temple or a forest floor eroded by the roots of trees. Creatures moving across broken ground can move at half speed without any problem. If a creatures moves across broken ground using a speed greater than half, that creature must succeed on a DC 12 Dexterity (Acrobatics) check or fall prone.

Deep Mud

This deep mud could occur underground, in swamps, or in plains or forests after a rain storm. Deep mud counts as difficult terrain. When a creature ends its turn in deep mud without moving from the spot where it started its turn, that creature is restrained. As an action a restrained creature can attempt to free itself and end the restrained condition with a DC 12 Strength saving throw.

Earthquakes

Earthquakes could shake the ground beneath the feet of any target. If combat occurs in an area of frequent earthquakes, at the end of each round, roll a d10. On a roll of 1-3 an earthquake occurs. Every creature standing on the ground must succeed on a DC 15 Strength saving throw or be knocked prone.

Lava Geysers

Lava geysers sit on the floor of volcanic tunnels occasionally spewing lava into the air. At the end of each round of combat roll a d20. On a roll of 11 or higher a random lava vent of your choice erupts spewing a line of lava 5 feet wide and 15 feet long into the air. Creatures in the line must make a DC 15 Dexterity saving throw. A target who fails takes 14 (4d6) fire damage, a target who saves takes half damage.

Lightning Storms

Lighting storms can occur with a downpour, but also in the heat of Summer months without any rain. At the end of each round of combat roll a d10. On a roll of 1-3 lightning targets a random 5-foot square of ground, making it difficult terrain. On a roll of 4-7 lightning targets a random creature wearing metal armor. On a roll of 8-10 lighting targets any random creature. A target creature must make a DC 15 Dexterity saving throw. A target who fails takes 28 (8d6) lightning damage, a target who saves takes half damage.

Sewage Spewers

In sewers covered pipes will sometimes open up and release pressurized bursts of sewage. At the end of each round of combat in the sewers pick a random pipe to open and release sewage. Creatures within 10 feet of the pipe must succeed on a DC 12 Strength saving throw or be knocked prone.

Sinkholes

Sinkholes can appear randomly and without warning on many different types of terrain. When combat occurs in an area that has sinkhole potential, roll a d10 at the end of each creature’s turn. On a roll of 1 a 20-foot deep sinkhole with a 5-foot radius appears centered on the creature. Creatures in the area of the sinkhole must succeed a DC 15 Dexterity saving throw or fall into the sinkhole, taking 7 (2d6) bludgeoning damage and landing prone. Creatures who succeed on the save end in an area of their choosing adjacent to the sinkhole.

Supernatural

Spellcasting trees, mind-altering rain, and grass with a mind of its own are all examples of supernatural hazards. They are the kind of thing you only see in fiction.

Acidic Waves

Some pools of acid have been magically enhanced by mages to be even more harmful than they seem. When battle occurs near a container of acid that has been enchanted with such magic, roll a d4 at the end of each round. On a roll of 1, a waves of acid spew from the pool, attacking all creatures in a 20-foot-radius. Creatures in the area must make a DC 15 Dexterity saving throw. Creatures who fail take 35 (10d6) acid damage. Creatures who succeed take half damage. Once the waves spew forth from an acid pool, you stop rolling to see if acid occurs at the end of each round for that pool.

Force Shockwaves

Ancient rituals of mighty power often cause the caster to give off shockwaves of residual magic energy. These rituals are the stuff of legend, beyond normal spells. At the end of the round while performing a powerful ritual, each creature within 30 feet of the caster must make a DC 15 Strength saving throw. Creatures who fail take 10 (3d6) force damage, are pushed back 10 feet and are knocked prone. Creatures who succeed take only half damage and are not pushed or knocked prone. These shockwaves stop once the ritual is complete or the caster is no longer able to perform the ritual.

Ghostly Ground

Sometimes burial grounds are long forgotten. The headstones and mounds wear down without ever leaving evidence that any bodies are decaying in the ground. The restless spirits of these dead sometimes manifest just for an instant to cause havoc before disappearing. When loud noise (such as battle) occurs on ghostly ground the spirits are awakened. At the end of each round, a spirit appears adjacent to a random creature on the ghostly ground and makes a melee attack against that creature with a +6 bonus to the roll. If the spirit hits, the attack deals 5 (1d4 + 3) necrotic damage and the target must succeed a DC 15 Constitution saving throw or become paralyzed for 1 minute. A paralyzed creature can repeat this saving throw at the end of its turn, ending the stunned condition on a success.

Grasping Grass

Some wander the world alone. For many this is a choice. Yet others wander because society has branded them a pariah. When these individuals die in loneliness craving friendship, their bodies and sorrow are absorbed into the ground. Grasping grass grows forth from the ground, holding onto the feet of any who pass by because the soul within hungers for company. When a creature ends its turn in grasping grass without moving from the spot where it started its turn, that creature is restrained. As an action a restrained creature can attempt to free itself and end the restrained condition with a DC 15 Strength saving throw.

Love Rain

It is said this rose-hued rain falls from the sky when an archfey takes a new lover. Each creature in the rain must succeed on a DC 10 Wisdom saving throw at the end of its turn or become charmed by the closest creature for 1 minute. A charmed creature can repeat this saving throw at the end of its turn, ending the charmed condition on a success.

Mage Trees

It is said these trees were planted long ago by a secret society of wizards who worshipped a vengeful spirit of nature. This spirit believed the spread of civilizations and development of land to be a blight. These mage trees were planted to destroy those who pillage the land. The spirit and the wizards have since faded into history, but the trees remain. Awakened by the sound of clashing steel, a mage tree acts at the end of each round. The tree casts a random cantrip from the table below against a random non-plant creature.

d4

Spell

1

Acid splash

2

Chill touch

3

Fire bolt

4

Ray of frost

Petrifying Swamp

Certain swamps are said to have areas cursed long ago by covenants of hags. The areas are usually marked by statues of various creatures sinking into the swamp. The magic of the terrain is activated when a creature engages in a hostile action, such as drawing a weapon or casting an offensive spell. Once the terrain is activated, each creature in the petrifying swamp must succeed on a DC 10 Constitution saving throw at the end of its turn or become stunned for 1 minute. A stunned creature still in the petrifying swamp must repeat this saving throw on the end of its turn. If it succeeds, the stunned condition effecting it ends. If it fails the creature is petrified. A creature is no longer petrified if it is removed from the swamp, cleaned, and untouched by the swamp for 1 hour.

Switching Mirror

These huge magic mirrors are often used to line the ceilings, floors, or walls of lavish palaces expecting invaders. The mirrors are also popular in the temple of trickster gods. During combat at the end of the round each creature who can see the mirrors must roll a d20. Creatures who roll the same number immediately switch places in a clockwise order.

War Ground

The blood which soaked into this ground from wars long ago has left a distinct red stain on the land. Creatures who stand on the ground deal maximum damage whenever they hit with a melee attack.

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11 Comments

I LOVE this list, James. Comprehensive & clever, with a great variety (though I think “Love Rain” could double as a Nicholas Sparks title about two strangers trapped in a monsoon). A particularly nasty DM (ahem Mike Shea ahem) could also combine these with one another or with particularly massive creatures for awesome effect… The Tarrasque arriving could set off an earthquake which could cause a sinkhole, force shockwaves could set off an avalanche, Tiamat’s arrival could cause lava geysers to erupt, etc. Some of these might also invoke the exhaustion mechanics (which are brutal in 5E)… like if you’re stuck under the avalanche for too long, trudging across too wide a swath of bones or deep mud, etc.

Also, with the avalanche in particular, I would also consider adding in some mechanics for fleeing the oncoming snow wall (perhaps using some of the mechanics from that awesome Give Chase article you wrote for EN World). You could even set up the whole encounter to be about the avalanche… scene 1 is exploration & a fight in a large echo-y area, trying to be quiet, ending with the last bad guy blowing a horn. Scene 2 is running from the avalanche, looking for places to take cover or flat-out fleeing. Scene 3 is digging out/finding one another again. Scene 4 is a fight with the ghosts disturbed when the avalanche ran over that cemetery. Scene 5 is trying to find anything to make a fire & stay warm that night after having been pounded with cold & necrotic damage.

Each turn you can see them, you choose between rolling and making a Charisma save. Pass the save and you can switch with another creature of your choice. Fail the save and you get switched with the least convenient creature.

[…] World Builder Blog – Simple Hazards by James Introcaso. In the second of his three posts, James provides numerous simple hazards that can be encountered in combat, both mundane and supernatural. At the end, he also provides a PDF with this information. […]